Field of the Invention
The present invention relates to coupled vanes of a turbine applied to an aeronautic engine for example, and a method of production thereof.
Description of the Related Art
On a turbine vane as one of components of a jet engine for example, in use, acts an intense stress due to strong centrifugal force or gas flow. Since particularly high strength as well as thermal resistance is therefore necessary for such a turbine vane, metal materials are generally used for production. While FIG. 13A is a general perspective view of a typical aeronautic turbofan engine and FIG. 13B is a general perspective view in which a part of its turbine rotor vanes is enlarged, because a strong centrifugal force C acts on the turbine rotor vane, the turbine rotor vane is in general produced from any of Ni-based alloys or such. Further, as shown in FIG. 13B, although a turbine rotor vane has a complex shape comprising a vane section 72, a platform section 74 elongated in a vertical direction relative to faces of the vane, a dovetail section 76 disposed at one end of the vane section 72, and a tip shroud section 78 elongated in a vertical direction relative to the faces of the vane at another end, it is readily produced by casting a metal material such as a Ni-based alloy. The similar applies to turbine stator vanes and any of them has a complex shape but is readily produced by using a metal material such as a Ni-based alloy.
Turbine vanes may be used either as single vanes or as coupled vanes. In a case of rotor vanes, tip shroud sections are mutually joined, thereby being made into coupled vanes. In a case of stator vanes, a shroud section (outer band section) and a platform section (inner band section) of each vane may be respectively joined to these counterparts so that coupled vanes are made, or coupled vanes are integrally formed by casting. FIG. 13C is a schematic perspective view depicting a turbine rotor vane of a coupled-vane structure, in which a coupled-vane 80 is comprised of vane sections 82, platform sections 84 elongated in vertical directions relative to faces of the vanes, dovetail sections 86 disposed at one ends of the vane sections 82, and tip shroud sections 88 elongated in vertical directions relative to the faces of the vanes at another ends. In this case, its shape comes to be more complex but can be produced by using an advanced mold.
And, in recent years, ceramic matrix composites (CMC), each of which is comprised of a ceramic fiber fabric and a ceramic matrix, are expected to be applied to turbine vanes. As ceramic matrix composites are superior in light of weight and thermal resistance, if they can be used as turbine vanes, it could be expected to reduce weight of engines and reduce fuel consumption rates.
Some proposals for turbine vanes to which ceramic matrix composites are applied and production methods have been so far brought forward. Further there have been proposals for turbine vanes of coupled-vane structures exemplified in FIG. 14 (see PTL 1 or 2 below for example). FIG. 14 is that in which four turbine stator vanes are coupled and the turbine stator vane 90 of a coupled-vane structure is comprised of vane sections 92a, 92b, 92c, 92d, an outer band section 94 and an inner band section 96 respectively elongated in vertical directions relative to faces of the vanes. Among these four vane sections 92a, 92b, 92c and 92d, to the outer band section 94 and the inner band section 96 applied is adhesive to bond them or they are mechanically connected.
U.S. Pat. No. 6,648,597 (PTL 1) and Japanese Patent Application Laid-open No. H07-189607 (PTL 2) disclose related arts.